Laptop doesn't know which display to use when docked/undocked

[Terry Polzin]

I am running xfce on F17 completely patched and current.

My laptop is a HP probook 6460b.  When I boot it docked the grub screen
appears on the external display.  When the boot has completed the
background screen is displayed on the external display. I get no login
prompt on the external display.  I press enter a couple of times the
login display will appear and I'll log in then the external display goes
dark.  I open up the laptop and it's display has the desktop on it and I
have to manually switch to the external display and discontinue use of
the laptop display.  If both displays are selected for use the whole
thing wants to act like a twin head setup which I don't want.

What do I have to do to get the laptop to use the external display when
docked and it's own display when it isn't automagically. To undock the
laptop I have to reverse the display procedure of course.  This also
makes it impossible to "undock and run" without making manual changes as
to which display to use.